Euryleptidae Lang, 1884

Litvaitis, Marian K., Bolaños, D. Marcela & Quiroga, Sigmer Y., 2019, Systematic congruence in Polycladida (Platyhelminthes, Rhabditophora): are DNA and morphology telling the same story?, Zoological Journal of the Linnean Society 186, pp. 865-891 : 882-883

Euryleptidae Lang, 1884

In Euryleptidae , our samples covered the genera Eurylepta , Cycloporus , Prostheceraeus and Maritigrella . Unlike Bahia et al. (2017), we recovered Cycloporus as a monophyletic genus. Morphologically, Cycloporus is distinguished from other euryleptids by the shape of the tentacles (small protuberances on the anterior margin) and by numerous small, peripheral vesicles surrounding the body margin, from which it derives its name. These vesicles are lateral branches of the digestive system that open to the exterior via pores ( Newman & Cannon, 2002). This morphological distinctness might be the reason for the low molecular support of Euryleptidae as a family, and the relationship of Cycloporus with euryleptids warrants further investigation.

Three species of Maritigrella formed a discrete clade. However, the two Caribbean species of Maritigrella cluster with Prostheceraeus . This apparent paraphyly led us to re-classify Maritigrella crozieri ( Hyman, 1939) and Maritigrella newmanae Bolaños et al., 2007 . Based on a distinct colour pattern of transverse stripes and the absence of uterine vesicles, Newman & Cannon (2000) erect the genus Maritigrella for a group of euryleptid polyclads from the Indo-Pacific. Relying on similar striped colour patterns and the absence of uterine vesicles, Newman et al. (2000) then synonymized and reclassified Pseudoceros crozieri Hyman, 1939 , Prostheceraeus zebra Hyman, 1955 and Cryptoceros crozieri Faubel, 1984 into Maritigrella crozieri ( Hyman, 1939) . Although the reclassification into Euryleptidae is warranted ( Pseudoceros belongs to Pseudocerotidae ; Cryptoceros has been abolished; Litvaitis et al., 2010), Hyman’s (1955b) description of Prostheceraeus zebra clearly states that the species is lacking uterine vesicles. Hence, the fact that uterine vesicles may be absent in some species of Prostheceraeus indicates that they are of little phylogenetic value in this group. Consequently, we here move Maritigrella crozieri to Prostheceraeus , to form Prostheceraeus crozieri comb. nov. Additionally, after a re-examination of our specimens, a comparison with Hyman’s (1955a) original description and holotype material and the results of our molecular analysis, we recognize Maritigrella newmanae as a junior synonym of Prostheceraeus floridanus .

Traditionally, morphological traits for the identification of euryleptids have focused on tentacle shape (pointed, slender vs. small anterior bumps), the presence or absence of marginal pores, the number of uterine vesicles (none, two or multiple) and diverse colour patterns. Characters of the male reproductive system are of little taxonomic value, because of their uniformity and resemblance to pseudocerotid systems. Although some euryleptids may be identified by unique colour patterns (e.g. some species of Prostheceraeus and Maritigrella ), the inadequacy of species-specific characters compels a reliance on molecular data for positive species identification, especially in Eurylepta .